In many processes it is necessary sequentially to connect different feed conduits and discharge conduits to process chambers or equipment. The standard approach is to use a plurality of conduits and valves to achieve the desired fluid distribution between the various chambers. However, as the number of feed and discharge conduits and/or the number of process chambers are increased, the use of conventional piping and valves becomes very cumbersome. Although the number of valves may be reduced through the use of multi-port valves at each process chamber, the complexities of the piping arrangement remain.
An alternative method is to mount the process chambers on a rotating carousel, and to use a rotary distribution device sequentially to connect the different feed conduits and discharge conduits to the process chambers. Although this method has significant advantages, and is widely used in the ion-exchange field, it has the primary disadvantage of requiring all the process chambers to be mounted on a rotating carousel. Rotating carousels are described in U.S. Pat. No. 4,522,726 and U.S. Pat. No. 5,676,824.
An alternative approach is to use a rotary distribution apparatus where the feed conduits, the discharge conduits, and the process chambers remain stationary. However in practice, for various reasons, these rotary distribution valves are not widely used.
U.S. Pat. No. 3,192,954 to Gerhold et al describes a rotary distribution valve. This valve comprises a cylindrical valve casing with a plurality of ports extending through the casing. A cylindrical rod-shaped plug is rotatable within the casing. Circular grooves are located in the casing or in the plug. A conduit communicates with each of the circular grooves and extends through the wall of the casing to the exterior of the casing. Recesses, corresponding in number with the circular grooves, are circumferentially spaced around the plug. The ports are spaced around the periphery of the casing so that each of the ports is in communication with each of the recesses at some point in the rotation of the plug. Passageways, corresponding in number with the circular grooves, extend through the plug. Each passageway continuously connects one of the recesses in the plug with one of the circular grooves.
U.S. Pat. No. 4,625,763 to Schick et al describes a disc-axial multiport valve which comprises a fixed stator assembly to which process fluid conduits are connected. A rotor is rotatably mounted within the fixed stator. A fixed distributor is connected to the fixed stator. Process chambers are connected to the fixed distributor. The process chambers are sequentially supplied with process fluid as the rotor is rotated within the fixed stator.
U.S. Pat. No. 5,478,475 to Morita et al describes a fluid distribution apparatus consisting of an upper fluid distributor and a lower fluid distributor with a plurality of processing chambers held and fixed between the upper and lower fluid distributors. This apparatus suffers from the disadvantages that it requires two distributors and it is difficult to fabricate, particularly because of the complex shape of some of the passageways. The rotary valve has internal passages, which means that the size of the valve increases as the number of process vessels connected to it increases. Furthermore, if the process configuration of the process vessels is changed, it may be necessary to change the passageways in the distributors. Thus the apparatus cannot easily be adapted to accommodate a different process configuration.